Outside of what PI might have, I'm not sure a wiring diagram is provided as part of the Owners package.
On my unit, I have a GFCI breaker in the main electrical panel that protects the kitchen, bath, sofa/dinette slide, the utility center and the outside outlets. A fault at any location will cause the breaker to trip and remove power from all the outlets. It works and is wired like a normal circuit with juction boxes and several branches. Unlike a GFCI outlet series that is wired 'one behind the other, line to load.
When you mention GFCI outlets in the triple slide being out....are these GFCI outlets or are they protected by a GFCI breaker? Are there other outlets not working within the unit or Is the triple slide the only ones out?
If no other outlets in the unit are out...have you checked the outlets with the slide extended and retracted. As the wires for the slide travel within the rams, might check the harness to ensure there isn't a problem there also.
Here is a LINK
to testing GFCI outlets that might help.